The echinocactus, or bisnaga, is also called "The Well of the Desert." It has a large barrel-shaped body which is covered with long spikes that are curved like fishhooks. It is full of sap that is sometimes used to quench thirst. By cutting off the top and scooping out a hollow, the cup-shaped hole soon fills with a sap that is not exactly nectar but can be drunk in an emergency. Men who have been in danger of perishing from thirst on the desert have sometimes been saved by this unique method of well digging. Greasewood, or creasote bush as it is sometimes called on account of its pungent odor, grows freely on the desert, but has little or no value and cattle will not touch it. Like many other desert plants it is resinous and if thrown into the fire, the green leaves spit and sputter while they burn like hot grease in a frying pan. The mesquite tree is peculiarly adapted to the desert and is the most valuable tree that grows in the southwest. As found growing on the dry mesas of Arizona, it is only a small bush, but on the moist land of a river bottom it becomes a large forest tree. A mesquite forest stands in the Santa Cruz valley south of Tucson that is a fair sample of its growth under favorable conditions. Its wood is hard and fine grained and polishes beautifully. It is very durable and is valuable for lumber, fence posts and firewood. On the dry mesas it seems to go mostly to root that is out of all proportion to the size of the tree. The amount of firewood that is sometimes obtained by digging up the root of a small mesquite bush is astonishing. It makes a handsome and ornamental shade tree, having graceful branches, feathery leaves and fragrant flowers, and could be cultivated to advantage for yard and park purposes. Its principal value, however, lies in its seed pods, which grow in clusters and look like string beans. The mesquite bean furnishes a superior article of food and feeds about everything that either walks or flies on the desert. The Indians make meal of the seed and bake it into bread. Cattle that feed on the open range will leave good grass to browse on a mesquite bush. Even as carnivorous a creature as the coyote will make a full meal on a mess of mesquite beans and seem to be satisfied. The tree exudes a gum that is equal to the gum arabic of commerce. The palo verde is a tree without leaves and is a true child of the desert. No matter how hot and dry the weather the palo verde is always green and flourishing. At a distance it resembles a weeping willow tree stripped of its leaves. Its numerous long, slender, drooping branches gracefully criss-cross and interlace in an intricate figure of filigree work. It has no commercial value, but if it could be successfully transplanted and transported it would make a desirable addition to green-house collections in the higher latitudes.